Dynamics of water vapour adsorption by a monolayer of loose AQSOA™-FAM-Z02 grains: Indication of inseparably coupled heat and mass transfer

Dynamics of water adsorption in an adsorption chiller (AC) determines the specific cooling power and the AC size. The dynamics, in its turn, strongly depends on the configuration of an adsorbent - heat exchanger (Ad-HEx). Here we considered the simplest, monolayer, configuration of the Ad-HEx and studied the water ad-/desorption dynamics as a function of the grain size (0.2-2.1 mm), temperature drop (16-36 degrees C), and pressure (7-47 mbar) for a commercial adsorbent AQSOA(TM)-FAM-Z02. The dynamics was measured by a Volumetric Large Temperature Jump method under typical conditions of isobaric stages of real AC cycle. It is found that the initial part of all kinetic curves is exponential and can be described by a single characteristic time tau. This time depends on the grain size R as tau-R alpha, where the index a is constant over the whole range of the grain sizes, and its value is 133 and 1.20 for adsorption and desorption runs, respectively. The alpha-constancy may indicate an inseparable coupling of heat and mass transfer in the monolayer configuration of AQSOA(TM)-FAM-Z02 adsorbent bed. For grains of about 2 mm size, quite acceptable initial power (>2 kW/kg) is obtained. Thus, the monolayer configurations may result in fast adsorption dynamics, reasonable specific power and compact AC units. (C) 2016 Elsevier Ltd. All rights reserved.